As is known in the washing of textiles, fabric softeners are used in the final wash cycle. The use of fabric softeners in this fashion reduces hardening of the washed fabric which is caused by drying. The handle, i.e. feel, of textiles treated in this way, such as hand and bath towels and also underwear and bed linen, is favorably influenced.
Prior art fabric softeners typically contain cationic compounds, for example quaternary ammonium compounds, which, as well as long-chain alkyl radicals, may also contain ester or amide groups. Such fabric softeners are described for example, in U.S. Pat. Nos. 3,349,033; 3,644,203; 3,946,115; 3,997,453; 4,073,735 and 4,119,545. The above mentioned components are added to the rinse bath on their own or in mixtures with other cation-active agents or neutral substances in the form of aqueous dispersions.
Frequent use is made of ammonium compounds that contain ester bonds, as described, for example, in EP-A-0 239 910 and U.S. Pat. Nos. 3,915,867; 4,137,180 and 4,830,771.
Ester compounds based on triethanolamine, such as N-methyl, N,N-bis(beta-C.sub.14-18 -acyloxyethyl), N-betahydroxy-ethyl-ammonium methosulfate, marketed under tradenames such as TETRANYL.RTM. AT 75 (trademark of KAO Corp.), STEPANTEX.RTM. VRH 90 (trademark of Stepan Corp.) or REWOQUAT.RTM. WE 18 (trademark of Witco Surfactants GmbH) are particularly widespread.
These esterquats have virtually replaced the previous raw materials distearyldimethylammonium chloride (DSDMAC) and imidazolinium quats throughout Europe. However, consumer requirements for these compositions vary considerably within this market.
In Northern and Central Europe, concentrates with contents of esterquats of 18-20% and a low viscosity of about 50-200 mPas are currently acceptable, while consumers in Southern and Eastern Europe prefer low concentrations of 3 to 10% by weight, in particular from 4 to 5% by weight.
The disadvantage which is criticized by consumers in the case of formulations with the low concentrations is the low viscosity and thus their consistency. Referring to the formerly used raw materials, a significantly higher viscosity is required in order to give these products a creamy, gentle appearance.
The viscosities of these products, which are desired or required to achieve the desired effect, are in the range from about 500 mPas or, preferably, above. This order of magnitude can be achieved without problem employing the traditionally used laundry softener raw materials (including DSDMAC) without the need of additional viscosity regulators. In the case of the esterquats, because of the different viscosity behavior of these raw materials, it has become difficult to achieve the desired high viscosities without additional expensive thickeners.
The disadvantages of using expensive thickeners include relatively high raw material costs and, as a result of additional stirring in and swelling of the thickeners, significantly extended production times.
Attempts already have been made to replace the partially hydrogenated fatty acids, which are used as standard in the preparation of esterquats and are based on alkanolamines and fatty acids, with completely hydrogenated fatty acids. According to experience, this should result in a significantly high viscosity. However, this is not the case to the desired extent.
It is thus even more surprising that the grade according to the present invention has unexpectedly positive viscosity behavior, which makes it possible to achieve the desired high viscosity without further additives.